Southeast Asia developed maritime trade from the early period due to the suitable physical and cultural conditions. The land consists of peninsular and archipelago, and located at the junction of the two monsoons in South China Sea and India Ocean. The people inherit cultural openness to receive outer influences positively. When Portuguese came to Southeast Asia in 16th century, the region had already enjoyed certain level of commercial development and sociocultural dynamics through the long time experience of interactions with outer world. The Portuguese contact to Southeast Asia was more of participation and assimilation than of conquest and rule experienced in South America. It was due to the higher level of spiritual and material civilization existed in Southeast Asia. Portuguese brought several new elements into Southeast Asia such as colonization and new weapons, Cartaz system and commercial monopoly, and Catholic mission and Casado policy. These new elements, however, did not impact much on the existing Maritime trade that played an important role to change the sociocultural structure of Southeast Asia. Even though Portuguese contact itself did not make significant differences in Southeast Asia, it was meaningful in a sense that it opened a path and left a model case for the more powerful Europeans who came soon after her.